The present invention relates to a driving force transmission device, a medium transport device, an image reading apparatus and an image forming apparatus.
A driving force transmission device is used in, for example, a drum-type photoengraving scanner. The driving force transmission device includes a toothed belt and a toothed pulley meshing with each other. Conventionally, vibration may occur at a starting position and a terminate position of meshing between the toothed belt and the toothed pulley. In order to absorb such vibration, there is proposed a toothed pulley including an inner ring portion, an outer ring portion, and vibration absorbers provided at a boundary portion between the inner ring portion and the outer ring portion (see, for example, Japanese Laid-open Patent Publication No. 62-274134).
In this regard, if the driving force transmission device is used in a scanner or the like, a change in load on the driving force transmission device may occur. In such a case, it is difficult to suppress a change in speed.